Hello Alexei,
Problem - you are talking about changing registrar, but in reality you describe changing of domain owner.
Yes you are right in that often a number of domain name variables change at around the same time.
Why (what for) is it allowed to transfer from one registrar to another with changing NS records and other owner information?
Usually it is NS records that change, as a transfer can be associated with moving a domain name to a new service provider for email or web hosting. It is often the change in other services that prompts the transfer request in the first place.
Why don't separate this 2 events - changing registrar, and changing domain owner/information? Is it any need in reality changing registrar with simultaneous changing domain information?
I agree with respect to "ownership" change that this should be separated by some time period from registrar transfer. Note that only the registrar transfer process is regulated by the ICANN agreements. Apart from changes in the identity of the legal holder of the domain name agreement, other details such as postal address, phone numbers and email addresses are often updated at the time of customer contact with respect to the transfer. Usually this information represents the most up-to-date contact information.
What should happen in normal situation: - someone requested transfer of domain (without real authorisation); - even if all checks pass and transfer was allowed, new registrar should maintain the same NS and other information as old one, so no real damage could happen; - domain owner received e-mail, see frauded transfer and disputed it (having domain in working condition on the new registrar); - new registrar OR old registrar OR VeriSign roll back transaction.
This is effectively what happened in the panix.com case. As soon as facts were verified the NS records were rolled back by the gaining registrar to their previous state. The issue was that it took hours to occur. It is a separate discussion as to whether the registry operator (Verisign in this case) should do this roll back in the case of a network outage in the absence of instructions from registrars. Regards, Bruce